Japanese Patent Application Laid-Open No. 2001-22470 discloses a notebook-type personal computer (hereinafter referred to as a laptop PC) provided with an illumination device (keyboard light) that irradiates a surface of a keyboard. The illumination device is realized by an LED holder in which an LED is housed. An upper edge of a display device extends like eaves with respect to a front surface of the display device, and the illumination device is attached to the upper edge. This configuration allows light rays from the LED holder to irradiate the keyboard below the LED holder.
In recent portable computers, a system which is a so-called flat design and in which a front surface of a peripheral margin of a display device and a front surface of the display device are located on the same plane has become adopted. In this case, since there is no structure such as eaves on the front surface of the display device, a keyboard light having a structure like that disclosed in Japanese Patent Application Laid-Open No. 2001-22470 cannot be adopted. Further, such a method in which an LED holder is supported by a spring structure so that the LED holder is sprung out of the inside of a housing and pushed back into the housing according to opening and closing of a cover of a laptop PC can be considered. However, the method is not preferable because the number of parts increases and an opening is formed on the front surface.
JP Patent No. 3982174 discloses a light irradiation apparatus constituted by a light source and a light guide plate. The light guide plate is configured so that a light ray that is incident from the light source is multiply reflected and emitted from between a perpendicular direction and a horizontal direction with respect to a bottom surface.
Japanese Patent Application Laid-Open No. 8-17209 discloses an illumination device embedded in a wall surface so as to illuminate a floor. The illumination device of Japanese Patent Application Laid-Open No. 8-17209 is configured so that when light emitted from a fluorescent lamp travels while repeating total reflection inside a cuneate light guide, the light gradually goes obliquely downward as it crosses over a critical angle. Further, Japanese Patent Application Laid-Open No. 8-17209 discloses that emission light is emitted at an output angle of 65 degrees±10 degrees to the normal line to the wall surface.
In the method of Japanese Patent Application Laid-Open No. 8-17209, a long light guide is necessary to use the repetition of the total reflection. However, such a long light guide is not suitable for mounting around a display. Further, light rays having large output angles (refraction angles), which can irradiate the area of the keyboard near the display, are not included. In view of this, the principle of Japanese Patent Application Laid-Open No. 8-17209 cannot be applied to the keyboard light. In a case where the light guide plate described in U.S. Pat. No. 3,982,174 is placed upside down to be used for the keyboard light, the light guide plate requires a length to allow multiple reflections between a front surface F and a rear surface R, and further, light rays having large output angles that can fully illuminate the keyboard, are not included. Thus, this light guide plate is also not suitable for the keyboard light for the same reason as Japanese Patent Application Laid-Open No. 8-17209.